A reminder of the need to protect workers from hazardous dust
On June 24, 2011 the Indian Express, an on-line Indian news outlet, published an article reporting a “new” occupational lung disease and implicating a polyacrylate powder, which “seemed to be at the nano-level.”
The article is based on an investigation published by the Peoples Training and Research Center, a voluntary organization raising awareness and providing training on occupational safety and health. It reports a cluster of five cases of workers with severe pleural and pulmonary disease, which developed within 10–12 months of working at a factory that manufactures and processes polyacrylate and other polymers for use in pharmaceuticals. It is not entirely clear from the report, but it appears that two workers had interstitial lung disease with pneumothorax; one worker had interstitial lung disease associated with severe restrictive impairment; one worker had at least one pneumothorax; and one worker died after developing a symptom complex of fatigue, anorexia, and breathlessness, but no additional medical information was available. The workers are reported to have labored under highly unsafe conditions. The report describes how unprotected workers were exposed to high levels of dust while operating grinding and sieving machines, bagging final product and handling filled bags of the ground polymer in a 10–12 work-hour day. They were given “ordinary masks,” aprons and plastic shoes. The dust is described as very hygroscopic (moisture absorbing) and sticky; a common behavior for this class of materials. By the end of the day, the workers were covered with dust. They had no laundry facilities to wash work clothes, and they described how compressed air and salt water were used to remove the sticky powder from clothes and body parts. All of the descriptions given in the article were relayed to the investigator by the workers. No quantitative evaluations of the massive exposures they endured are available.
Numerous animal toxicity studies to investigate adverse health effects due to inhalation exposure to respirable particles of polyacrylates have been conducted in the past. For example, one study showed that while exposure of hamsters to low concentrations of polyacrylate dust in particle sizes capable of reaching deep lung structures did not cause pulmonary fibrosis, exposure to high concentrations of these particles did.1
In the U.S. there are neither OSHA permissible exposure limits nor NIOSH recommended exposure limits for polyacrylate dusts. However, the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has set a permissible exposure limit (MAK) for respirable fraction of polyacrylate powders at 0.05 mg/m3.2 The Dutch Expert Committee on Occupational Health Standards (DECOS) reviewed the MAK and issued the same recommendation; namely 0.05 mg/m3 as being protective for workers health.3 Similarly, industry associations recognize polyacrylate powders as potential respiratory tract irritants and recommend an eight-hour exposure limit of 0.05 mg/m3, as measured as the respirable fraction of the aerosol.4 In addition, some manufactures recommend on their Material Safety Data Sheets handling these powders as eye and respiratory tract irritants and providing local exhaust ventilation, wearing safety glasses, impervious gloves and, when necessary, respirator with a high efficiency filter in order to reduce exposures.5 Methods for measuring concentration of polyacrylate powders in the air are available.6
The size distribution of dust particles inhaled by the Indian workers is unknown, so it is not possible to determine if inhaled nanoparticles produced by the grinding process played a role in their disease process, as suggested by the media. Several previous reports in the lay and scientific literature have initially implicated manufactured nanoparticles as agents causing adverse health effects, but failed to demonstrate a causal link. The “Magic-Nano” case in Germany in 2006 7 and the “print plant” case in China in 2009 received the most media coverage.8 In the “Magic-Nano” case, the German government and a product manufacturer later showed that the product did not contain nanoparticles. They related adverse respiratory effects observed in users of Magic-Nano to solvent in the spray solution. In the “print plant” case, workers suffered from pleural and pericardial effusions; pulmonary inflammation and fibrosis; and pleural foreign-body granulomas after handling complex mixtures of chemicals including polyacrylate particles. However, no further studies have been conducted to characterize nanoparticles found in the lungs and in workplace environment and no further toxicological reports have been published to link specific agents present in the workplace environment to the observed adverse health effects.9 In both cases, consumers or workers were exposed to high concentrations of chemical mixtures, which could have been avoided by implementing adequate exposure mitigating measures and changes in application processes.
Regardless of the role of nanoparticles in this cluster of occupational lung disease in India, the outbreak highlights the ongoing dangers to workers handling active, fine powdered materials in the workplace and the critical importance of implementing adequate protective measures. Effective application of the hierarchy of controls elimination of hazardous materials and substitution of safer ones when available; engineering controls to prevent exposures; administrative controls, including safe work practices; and appropriate use of personal protective equipment are all important elements in the control of worker exposures when handling fine dusts. Furthermore, workers must be provided with proper training and access to appropriate medical screening and surveillance programs. Consistent implementation of these basic measures is critical to preventing occupational lung diseases, whether from dusts known to be hazardous or from emerging exposures whose toxicity remains unclear, such as engineered nanoparticles. It is only in this way that tragedies such as the one reported in the Indian article can be made a thing of the past.
Dr. Murashov is a Special Assistant for Nanotechnology to the NIOSH Director. He is a member of the U.S. Nanoscale Science, Engineering and Technology sub-committee and. leads projects on nanotechnology safety and health in the International Organization for Standardization, the World Health Organization and the Organization for Economic Co-operation and Development.
Dr. Geraci is a Supervisory Physical Scientist in the NIOSH Education and Information Division and is the Coordinator of the Nanotechnology Research Center. He represents NIOSH on the NNI Subcommittee on Nanoscale Science, Engineering and Technology (NSET) and on the Nanotechnology Health and Environmental Implications workgroup (NEHI)
Dr. Weissman is a pulmonary diseases physician. He is the Director of NIOSH Division of Respiratory Disease Studies and Manager of the NIOSH Respiratory Diseases Research Program.
- McGrath J.J., Purkiss L., Eberle M., McGrath W.R. 28-day inhalation study of a cross-linked polyacrylate superabsorbent in the Hamster. J Appl Tox 1994, 14(4):269-273
- The Dutch Expert Committee on Occupational Standards (DECOS-Committee). Dutch MAC Document on CAS: 9003-01-4 as published in the “Staatscourant”, 30 November 2000, No233, page 20
- McCormack P., et al. Measurement of Respirable Superabsorbent Polyacrylate (SAP) Dust by Ethanol Derivatization Using Gas Chromatography-Mass Spectrometry (GC-MS) Detection. J. Occ. Env. Hyg. 2011, 8:215-225
- Wolinsky H. A recent scare involving nanotech products reveals that the technology is not yet properly regulated. EMBO reports (2006) 7, 858 861, http://www.nature.com/embor/journal/v7/n9/full/7400799.html
- Song Y. Li X, Du X. Exposure to nanoparticles is related to pleural effusion, pulmonary fibrosis and granuloma. Eur Respir J 2009, 43:559-567
- NIOSH Science Blog: Occupational Disease and Nanoparticles
Visit the NIOSH website for more information on nanotechnology research at NIOSH.